This invention pertains to the art of electric lamps and more particularly to filament lamps or arc lamps in which an envelope is hermetically sealed from the external environment. The invention is applicable to electric lamps of this type employing molybdenum sealing foils hermetically sealed in vitreous material where the molybdenum sealing foil interconnects inner and outer leads. However, it will be appreciated that the invention has broader applications and may be advantageously employed in other environments and applications.
Double ended electric incandescent and arc discharge lamps typically employ a vitreous envelope in which a pair of metal inner leads have at least one end that extends into a gas filled cavity of the envelope. A second end of the inner lead is received in the vitreous material and is connected to a sealing element, preferably a sealing foil, that forms a hermetic seal with the envelope. The sealing foil is a thin, planar construction that interconnects the inner lead with an outer lead which, in turn, is connected to a power source. The sealing foil is usually formed from molybdenum having a thickness on the order of approximately 2 mils in order to form an effective hermetic seal with the envelope, typically constructed of a quartz material. Of course, it is understood that other refractory materials than molybdenum can be used to form the sealing foil, such as tungsten, platinum, or palladium.
A double ended lamp of this type, although widely used and commercially successful, occasionally encounters problems because of its structural configuration. Specifically, the elongated configuration of the double ended envelope on occasion makes it difficult to integrate into the overall lighting system.
It is also difficult to provide an effective mount for an elongated double ended envelope. Specially designed mounts are necessary to hold opposite ends of the double ended lamp and in a manner that does not interfere with effective operation of the lamp.
Still another concern with an elongated double ended envelope is that it is not as robust or sturdy as desired. Due simply to its configuration, the envelope presents an arrangement that is unsupported over a large length. Likewise, mounting wires used to secure the double ended lamp are elongated which leads to increased natural frequencies which adversely affects stiffness of the lamp assembly. Accordingly, the envelope is sensitive to damage that may result from shipping, installation, or even in use depending on the particular end use of the lamp.
For certain applications, it may be important to orient the arc or filament in a particular direction, even though it is desired that the remainder of the lighting system is preferred to be oriented in a different direction. For example, it may be desirable to position the arc or filament in a vertical direction. Simultaneously, there may be a competing desire to locate the reflector in a horizontal direction. Thus, it is important in selected applications to be able to position the axis of the filament or arc generally perpendicular to the axis of the reflector.
It has thus been deemed desirable to increase the sturdiness of the mounting arrangement, make the lamp adaptable to a wider array of configurations, and provide the option of orienting the filament/arc generally perpendicular to the reflector.